Hey, I'm building a continuity tester as a project which will detect different levels of resistance.
For example, an LED will light up when less than 10 ohms is detected, and another will light up when less than 100 ohms is detected.
Each scale (less than 10 and less than 100) will be built from a comparator, which will compare a set calculated voltage (say, 0.9v) against the voltage produced with the external measured resistance connected (using ohms law).
I've got each comparator to work with separate switches, the problem arises when i attempt to connect the two op amp circuits to a single switch that will simulate the two probes (Bottom left of the circuit).
I see why it is happening, i'm basically connecting the two circuits together which interferes with the resistances, but i was wondering if anyone on here knew a way around it? I dont think there is, but there may be a method that i'm not aware of.
Thanks for any help, and sorry if i'm not explaining it properly, i'm a beginner at electronics to be honest.
For example, an LED will light up when less than 10 ohms is detected, and another will light up when less than 100 ohms is detected.
Each scale (less than 10 and less than 100) will be built from a comparator, which will compare a set calculated voltage (say, 0.9v) against the voltage produced with the external measured resistance connected (using ohms law).
I've got each comparator to work with separate switches, the problem arises when i attempt to connect the two op amp circuits to a single switch that will simulate the two probes (Bottom left of the circuit).
I see why it is happening, i'm basically connecting the two circuits together which interferes with the resistances, but i was wondering if anyone on here knew a way around it? I dont think there is, but there may be a method that i'm not aware of.
Thanks for any help, and sorry if i'm not explaining it properly, i'm a beginner at electronics to be honest.